Introduction to Cerebral Visual Impairment and Cerebral Palsy

This article or area is currently under construction and may only be partially complete. Please come back soon to see the finished work! (27/11/2023)

Original Editor - Ewa Jaraczewska based on the course by Angela Kiger

Top Contributors - Ewa Jaraczewska, Jess Bell and Kim Jackson  

Introduction

Cerebral visual impairment (CVI) occurs in children with cerebral palsy (CP) or developmental delay. Children with CVI have been frequently diagnosed with cerebral palsy. Despite the importance of early diagnosis, there is no standardised assessment tool to diagnose CVI and one referral criteria guideline. The challenge in early diagnosis comprises a wide range of visual dysfunctions present in CVIs. They include central and peripheral vision dysfunction, dysfunctions in movement perception, gaze control, visual guidance of movement, visual attention, attentional orientation in space, visual analysis and recognition, visual memory and spatial cognition, which can affect a child's learning and social interactions. This article presents an overview of CVI and its relationship with cerebral palsy.

Definitions

Cerebral Visual Impairment

Cerebral Visual Impairment (CVI) is “a verifiable visual dysfunction, which cannot be attributed to disorders of the anterior visual pathways or any potentially co-occurring ocular impairment.”

Cerebral Palsy

Cerebral Palsy (CP) "describes a group of permanent disorders of the development of movement and posture causing activity limitation, which is attributed to non-progressive disturbances that occurred in the developing fetal or infant brain."

Brain Involvement in Vision

"It is estimated that over 50% of the brain is involved in vision processing." --Angela Kiger

The following example explains the process of the brain controlling the eyesight:

Example: the child plays the game of ball catching:

• The child sees the ball
• The frontal lobe of the brain decides about taking the action of ball catching and decides about its strategy.
• The occipital lobe process the information received through the eyes. It passes the processed image data to the posterior parietal lobes via the superior longitudinal fasciculi.
• The middle part of the temporal lobe supports this process, together with the posterior thalamus and superior colliculi, facilitating visual search and visual guidance of movement.
• The ball is identified and chosen for the target.
• The parietal lobe gauges the distance between the child's hands and the ball. If this is not the child's first involvement in this game, the temporal lobe takes part in the process as it controls memory. It subconsciously reminds the child that their hands are used to catch the ball, that he needs to reach out, and that his body needs to adjust.
• The temporal lobes via a bundle of nerve fibres on each side, process the local and detailed visual feedback.
• The child involves his cerebellum to adjust his actions' timing and balance.

Epidemiology

• CVI affect at least 3.4% of children. However, the number may be higher as many affected children go unidentified.
• More than 50% of children with learning difficulties who attend special schools have CVI.
• CVI is present in 2 per 1000 live births and 19 per 1000 live births for infants born at 20-27 weeks gestation, with subcortical damages being more common in preterms.
• Most common cause of permanent vision loss in children 1-3 years old.
• Almost 50% of the children diagnosed with a visual impairment have CVI.
• 56% of individuals with CVI have additional disabilities.  

Aetiology

The aetiology of CVI in children can be either prenatal, perinatal or postnatal:

Prenatal:

• hydrocephalus
• congenital central nervous system malformation
• metabolic disorders
• genetic/chromosomal disorders

Perinatal:

• hypoxic ischemic injury
• trauma
• cardiac arrest

Postnatal:

• meningitis
• encephalitis
• brain tumours
• cerebrovascular accidents
• neonatal hypoglycemia
• seizures
• periventricular leukomalacia

Brain Damage and CVI

The brain damage in patients with CVI can be categorised as subcortical, cortical or both.

Brain lesions resulting in CVI can affect the following parts of the brain:

• the posterior visual pathways (the visual cortex of the occipital lobe)
• the optic chiasm ("part of the brain where the optic nerves cross" )
• lateral geniculate bodies (a structure in the thalamus)
• optic radiations ("key white matter structures that cross the temporal lobe")
• primary visual cortices (part of the occipital lobe that processes visual information)
• the middle temporal lobes
• the visual association areas

The following video explains the role of the visual association areas:

Characteristics of CVI

The symptoms of CVI and the severity of visual impairment vary in children. They can affect the following:

• sensory visual function: it enables an individual "to be aware of colour, light level, contrast, motion and other visual stimuli".
• oculomotor function: "the ability to use the eyes systematically to efficiently scan and locate an object in the field of vision."
• visual-motor function: "integration between visual perception and motor skills."
• cognitive visual function: ability to analyse and process visual information.

Other characteristics of CVI are:

• can occur in isolation or association with eye or optic nerve damage
• when thalamus is involved than the lack of vision tends to be profound

Symptoms of CVI

The child with CVI diagnosis presents with the following:

• Often have a normal or near normal eye exam
• Have a history or presence of a neurological disorder
• Behavioral responses to visual stimuli unique to CVI
• Difficulty to sustain gaze
• Head tilted slightly forward and tilted to the side is a common presentation

Behavioural Changes

Children diagnosed with CVI can demonstrate specific behavioural signs:

• short visual attention span
• markedly fluctuating visual performances
• the need for time, environmental stability, and repetition of items to obtain the best response

Diagnosis and Assessment

Admission Referral

Children are referred to a specialist or specialists for assessment of visual impairment because:

• the parents are concerned about child's visual functioning
• they have an increased risk on CVI
• they have intellectual disability or syndrome who can be screened on visual functioning.

Multidisciplinary Team

The multidisciplinary team for CVI diagnostics is necessary for accurate and timely diagnosis. The team should include at minimum:

• pediatric ophthalmologist
• pediatric neurologist
• orthoptist or optometrist
• neuropsychologist.

After ophthalmological and orthoptic examination the ophthalmologist should organize multidisciplinary meetings to discuss the results and the possibilities for further assessments, if necessary. For instance, the ophthalmologist should discuss with the neurologist (or pediatrician with specialization in neurology) referral criteria if a neurological diagnosis is suspected or a neurodegenerative diagnosis is in the differential diagnosis.

Follow-up Referral

The assessment results should be discussed with all members of the multidisciplinary team. Based on the outcome, the child can be referred to:

• Vision Teacher & Developmental Therapist Vision Specialization in CVI
• Rehabilitation center or a specialized center
• School for visually impaired children if there is evidence of CVI

Assessment Tools

questionnaires, functional vision assessment (CVI Range), neuropsychological tests of visual perception, and eye tracking. Eye tracking shows promise for visual assessment in both clinical and research settings because it is objective and quantitative, with the ability to assess diverse visual parameters.

Resources

• bulleted list
• x

or

1. numbered list
2. x